The Long-term Variations of Ozone and Nitrogen Oxides in Suwon City during 1991 similar to 2012

Abstract

The long-term variations of ozone and nitrogen oxides in Suwon city, the capital of Gyeong-gi province, were examined from 1991 to 2012. In this period, the annual average O-3 concentration increased from 13.8 ppbv to 22.7 ppbv and that of 99th percentile increased from 58.0 ppbv to 80.0 ppbv. The monthly average and 99th percentile of O-3 concentrations were the highest in June. The increase in O-3 concentration was the greatest in early summer (May and June) before monsoon season began. While the concentrations of NO and NOx have gradually decreased since 2000, NO2 remained unchanged. As a result, NO2/NOx ratio increased from 0.5 to 0.73 in 2012. The monthly NO2/NOx ratio was the highest in early summer, when monthly average O-3 concentration was the highest. It suggests that the enhanced NO2/NOx ratio is intimately coupled with increase in O-3 for the last two decades in Suwon.